Low‐energy charge‐transfer state and optical properties of Eu ³⁺ ‐doped GaN

Abstract

We argue that the charge-transfer state of Eu 3+ due to an electron transfer from N to Eu plays important roles in the luminescence properties of GaN : Eu 3+ grown by gas-source molecular beam epitaxy. On the basis of the excitation spectrum of the Eu 3+ luminescence, the excitation mechanism of Eu 3+ under the GaN interband excitation is interpreted in terms of the energy transfer from the above charge-transfer state. The intra-4f shell 5 D 0 -7 F 2 transition strength of Eu 3+ in GaN, which is responsible for red luminescence, is large compared with those of most Eu 3+ -doped oxide materials. This fact can be attributed to the low-energy position of the charge-transfer state of Eu 3+ in GaN.

Lanthanide impurity level location in GaN, AlN, and ZnO

“…Tanaka et al [28] suggested this quenching mechanism in GaN. Since the energy of valence band electron to Eu 3+ charge transfer increases from 3.15 eV in GaN to 3.5 eV in AlN, we expect that the energy barrier for quenching via the CT band should increase with about 0.35 eV.…”

“…2 we need information on the energy of charge transfer to Eu 3+ . We used a value of 3.15 eV as derived from [28,6]. Fig.…”

Study of GaN:Eu[sup 3+] Thin Films Deposited by Metallorganic Vapor-Phase Epitaxy

“…This peak has been attributed to a charge transfer transition in nitride lattices. 8,32,33 We tend to favor its assignment to a defectrelated absorption for the following reasons. 25 The band is nearly nonexistent for the 619 nm excitation.…”

Rare-earth defects in GaN: A systematic investigation of the lanthanide series

“…Only very limited discussion of these optical transitions is currently available in the lit-erature. For example, there was suggestion of a Eu related, broad "charge-transfer" excitation band centered at about 3.0-3.2 eV above the VBM in the photoluminecence excitation (PLE) spectra of Eu-doped GaN [10][11][12][13]. However, given the fact that a similar excitation band centered at ∼3.1 eV was also observed in the PLE spectra of Er-implanted GaN [38], further investigations are needed to confirm the origin of such transitions.…”

“…McHale et al [9] reported that the occupied Gd, Er, and Yb 4f states are deep in the valence band. There was also suggestion of a broad "charge-transfer" excitation band associated with the Eu * khang.hoang@ndsu.edu defect in Eu-doped GaN [10][11][12][13]. On the basis of an empirical model, Dorenbos and van der Kolk proposed a scheme with the location of all lanthanide impurity levels in GaN [14].…”